The future of multi GPU

[Carfax83]

Is it just me, or does it seem like multi GPU technology is going out of style these days? :\

Although multi GPU has been around for a very long time, it seems as though fewer and fewer developers are willing to support it in their games. And even when it is supported, it's plagued with issues like stuttering, flickering textures and other anomalies.

Watch Dogs is a great example. Admittedly a terrible engine, but Ubisoft managed to fix the stuttering issues in the last patch and the game now runs smoothly......on single cards that is. For SLI users, it stutters like porky pig! D:

To fix whatever the problem was, required or resulted in them breaking SLI. And I doubt Ubisoft will release another patch to fix the SLI problem as PC gamers with SLI are a small minority compared to single card users.

AC Unity and Dragon Age Inquisition both have texture flickering issues with SLI. The former has a great unofficial workaround that fixes the problem, but Ubisoft has not seen fit to release an official patch to solve it despite the clamoring on their forums. DAI had horrible texture flickering on launch, and it took a few driver revisions to ameliorate it. Other games such as Far Cry 4, and even the newly launched Dying Light also suffer from mGPU associated issues, but I can't personally verify that as I don't have those games myself.

Some might say this sort of thing is to be expected though, a reasonable trade off for nearly doubling GPU performance. And I would agree. As a long time SLI user, I've grown accustomed to having to wait a little longer for my games to play optimally. And 95% of the time, the problems are eventually resolved whether through driver revisions, updated profiles and or patches.

But what would happen if future game engines nix support for multi GPU entirely? If developers are already struggling now with proper implementation, how will they fare when the engine itself has no native support?

We are already at that stage. Epic's Unreal Engine 4 (a major 3D engine thats going to have very wide adoption) currently has no native support for AFR based multi GPU rendering, due to how the engine is designed. In Unreal Engine 4, each rendered frame uses data from the previous frame to complete the render, which just isn't AFR friendly.

It may still be possible to implement mGPU support, but I doubt the results and quality are going to be as good as what we're getting now; and what we're getting now leaves much to be desired for the most part..

Which leads me to my next question. At present I have GTX 970 SLI, but with the VRAM, ROP and L2 cache fiasco I am debating returning them for a refund or a credit if I'm able, and using that money towards buying the fastest single GPU card I can get to handle 1440p max quality at 60 FPS in the latest titles..

No current card can fulfill those requirements, but in the next couple of months I'm anticipating the release of NVidia's GTX 980 Ti, Titan X and AMD's 390x which should be much more capable. So assuming I'm able to get a refund/store credit on my GTX 970s, what do you think I should do?

You think abandoning SLI is a good move at this time, or should I stick with it? If I stick with it, I'd most likely upgrade to GTX 980 SLI..

 

[desprado]

That is why i sold my GTX 780 Ti SLI and 1440p screen and i am back to 1080p with GTX 980 but i have to agree that gaming is far smother than GTX 780 Ti SLI.

 

[Black Octagon]

I also feel like graphics cards are more expensive than they used to be, so getting 2 or more feels like a bigger call than it did back in, say, 2005. Haven't looked up numbers and adjusted for inflation, though

 

[tential]

Not only is mGPU support going but it also takes a LOT more GPU power I feel for very very little increase of IQ.

If I was you though I'd go GTX 980 SLI. My gut feeling tells me you won't be as happy after learning this new info. My gut feeling also tells me that you wouldn't be happy using R9 290x CF for $560 as a stopgap until the GTX 980Ti/R9 390x (I know how much you like Nvidia after all).

So I'd say go with GTX 980 SLI, then sell it for a small loss and upgrade to the GTX 980 Ti SLI or the AMD 390x (if it's just so good you can't help yourself) if you feel like you're missing something.

 

[Carfax83]

That is why i sold my GTX 780 Ti SLI and 1440p screen and i am back to 1080p with GTX 980 but i have to agree that gaming is far smother than GTX 780 Ti SLI.

So is it really that much smoother going back to single card? I haven't had a single card setup for almost 7 years!

In all fairness though, when SLI works, it works really well and to me frame rates were very smooth. The only time I could ever detect microstuttering was when V-sync was disabled. With V-sync enabled however, gameplay was almost always very smooth barring some catastrophic exceptions like Watch Dogs.

 

[monstercameron]

kinda want to see sfr more, forget better fps and go with smoother frametimes. Any idea if ue4 supports sfr?

 

[desprado]

So is it really that much smoother going back to single card? I haven't had a single card setup for almost 7 years!

In all fairness though, when SLI works, it works really well and to me frame rates were very smooth. The only time I could ever detect microstuttering was when V-sync was disabled. With V-sync enabled however, gameplay was almost always very smooth barring some catastrophic exceptions like Watch Dogs.

It is much smother and less fps drops and no microstutter and no waiting for SLI profile or patches to fix to performance.

 

[tential]

Also, it's the beginning of a new generation. As devs get used to developing for the Xbone/PS4 they'll get through those consoles quicker and will be able to dedicate more time to making a PC release work.

Also maybe they'll eventually give up on Gameworks which I feel is associated with terribly optimized releases for PC.

 

[Carfax83]

Not only is mGPU support going but it also takes a LOT more GPU power I feel for very very little increase of IQ.

If I was you though I'd go GTX 980 SLI. My gut feeling tells me you won't be as happy after learning this new info. My gut feeling also tells me that you wouldn't be happy using R9 290x CF for $560 as a stopgap until the GTX 980Ti/R9 390x (I know how much you like Nvidia after all).

So I'd say go with GTX 980 SLI, then sell it for a small loss and upgrade to the GTX 980 Ti SLI or the AMD 390x (if it's just so good you can't help yourself) if you feel like you're missing something.

I honestly would definitely consider AMD at this point, but not for crossfire. AMD's power draw and DX11 driver overhead are just too high, and crossfire amplifies that. Also, fewer games have crossfire support compared to SLI.

If I did go AMD, it would be the 390x. I'm hoping it's a great card, because NVidia needs to be checked on their prices and more options is always a great thing.

 

[Carfax83]

kinda want to see sfr more, forget better fps and go with smoother frametimes. Any idea if ue4 supports sfr?

No idea, but I doubt it. I can't even recall the last time I saw a game support SFR. AFR has higher performance and fewer drawbacks with implementation, which is why it became so dominant.

Heck, NVidia doesn't even have SFR mode in their driver control panel any more.

 

[tential]

I honestly would definitely consider AMD at this point, but not for crossfire. AMD's power draw and DX11 driver overhead are just too high, and crossfire amplifies that. Also, fewer games have crossfire support compared to SLI.

If I did go AMD, it would be the 390x. I'm hoping it's a great card, because NVidia needs to be checked on their prices and more options is always a great thing.

I doubt the 390x would give you more performance than GTX 970 SLI.
Considering how many games are "Nvidia" sponsored games, you're more likely to be happy with gTX 970 SLI vs a singular 390x.

As for CPU utilization overhead with CF...
Look at your CPU again. I highly doubt it's something you have to worry about.

 

[bystander36]

Do you think the CF/SLI issues could be from using unified code built for the console first? Any graphic techniques they use in that engine that doesn't work well with CF or SLI, is going to be a problem.

 

[Magic Carpet]

I did go AMD, it would be the 390x. I'm hoping it's a great card, because NVidia needs to be checked on their prices and more options is always a great thing.

Ya, seems like a good card. Can't wait.

According to all sources thus far, the R9 390X will have 4x 1GB/1024 bit wide/~1.2 GHz/4-layer HBM RAM modules for a bit over 600 GB/s bandwidth, which sounds pretty awesome thus far. Unfortunately, HBM modules will not exceed 1GB each for at least another year, so there will be no 8GB variant of the 390X, ever, even as we see 4k UHD stuff start to take off.

 

[Carfax83]

I doubt the 390x would give you more performance than GTX 970 SLI.

I don't necessarily need more performance, but it would be nice if I could get similar performance. With all the efficiency improvements, GCN 1.2 Fiji XT core looks to be pretty damn potent, and it just might tempt me to go AMD.

At the very least, it will hopefully pressure NVidia to lower their prices on the GM200 parts.

As for CPU utilization overhead with CF...
Look at your CPU again. I highly doubt it's something you have to worry about.

Thats not the point. Even with a powerful CPU, CF doesn't scale as well as SLI in CPU bound situations unless Mantle is used. The reason is because NVidia's DX11 drivers have better multithreading support, and is specifically optimized for low overhead when it comes to draw calls.

BF4 is a good example. Just look at how NVidia is able to compete favorably with AMD despite the latter having access to a lower level API..

 

[Carfax83]

Do you think the CF/SLI issues could be from using unified code built for the console first? Any graphic techniques they use in that engine that doesn't work well with CF or SLI, is going to be a problem.

I doubt it. MultiGPU support is usually integrated into the engine itself to my knowledge. So either an engine supports it or it doesn't.

Also, whilst the PS4, Xbox One and PC share some code, the PC version should have it's own rendering path I would think, as it uses a different API compared to what the consoles use.

 

[destrekor]

It's still going to be awhile before any single-GPU setup can run 4K at full detail for a vast majority of games. Some game engines are either amazing at resource allocation and the effective use of multi-core CPUs, like BF4, while others aren't. Even then, I think we'll be seeing new games or new engines that are efficient with hardware yet still push the IQ boundary beyond the current hardware.
The idea of multi-GPU is that it keeps hardware "in the fight" for longer, whereas a card like the GTX 980 might be incapable of handling 4K in the best AAA engines by the end of 2015 (it can't handle some games now, so...).

Some people just want more than the "standard" these days, which tends to be 1080/1200p or perhaps even 1440/1600p. 4K and triple-monitor surround resolutions are still at the enthusiast level. The best someone can do for single-GPU is a card like the latest Titan of the current chip generation (so, Titan II or whatever the first fully-enabled GM200 is called), and that won't really do it all that well for all upcoming or current games, though I hope it can for most.


Has anyone seen any recent discussion of UE4 and multi-GPU? That will be a major downer if THAT engine is one of the latest to not support multi-GPU. I like the performance and IQ potential of these new engines, but that seems like trending backward, considering these very engines demand the performance potential of multi-GPU for high resolutions.

 

[therealnickdanger]

I think SLI/CF would be cooler if they could find a way to aggregated VRAM instead of mirroring it. I'm actually really surprised that hasn't happened yet... it's only been 17 years since the Voodoo 2...

 

[Pottuvoi]

Mantle and hopefully DX12 allows/forces developers to create their own method for multi GPU rendering.

 

[bystander36]

I doubt it. MultiGPU support is usually integrated into the engine itself to my knowledge. So either an engine supports it or it doesn't.

Also, whilst the PS4, Xbox One and PC share some code, the PC version should have it's own rendering path I would think, as it uses a different API compared to what the consoles use.

What has been described by some dev's, is that they use the same code for all platforms for rendering at the high level. And at some point in the code, where things go from high level graphics calls, it splinters off to platform specific code. Much like how they describe Mantle's thin layer, between the hardware and API.

 

[wand3r3r]

I've been satisfied with 290x crossfire and based on the reviews it should be excellent with the new XDMA technology (worth a quick read) and frame pacing.

Where I have thoroughly enjoyed having crossfire was with 4k. It was smooth and didn't require much compromise (very high settings) and looks amazing. I don't know if I will go dual card on my next setup, primarily due to the fact I bought my current cards with mining in mind. I will never go for a card as loud as the reference cards are though, that is my only negative factor (negated with aftermarket cards). The power consumption has never been noticeable and I think it's way overblown simply to market a current strong point.

I read about a lot of dual card issues but I guess my games have been limited to those that work pretty well. I haven't played any of the latest Ubisoft/Gameworks games and they definitely have the image of being the least optimized and buggiest games in recent times.

I guess it comes down to what games you play, and at what resolution. Personally I would never settle for the 970 deception and it would always bug me knowing the absurd compromise they have used to get the 4 GB sticker.

 

[5150Joker]

I'm currently playing Dying Light (gorgeous and fun game) at 1440p maxed out using SLI and it's working exceedingly well, especially at 144 Hz + G-Sync. All my other games work great too (e.g. BF4, Alien Isolation, FC4 etc). SLI/Crossfire aren't going anywhere, if anything they are needed more than ever with 4K becoming a thing.

 

[kasakka]

With 1440p and 4K becoming more common I don't see multi-GPU going anywhere. If anything, I'd like to see more dual GPU cards instead of having two separate ones. I'm currently on GTX970 SLI and apart from some missing SLI bits on release, most games work fine with it. I just wish Nvidia fixed some of the missing new features like MFAA and DSR not working on SLI despite being the perfect platform for those.

For 1080p there are already plenty of cards that can run most games at good framerates.

 

[destrekor]

With 1440p and 4K becoming more common I don't see multi-GPU going anywhere. If anything, I'd like to see more dual GPU cards instead of having two separate ones. I'm currently on GTX970 SLI and apart from some missing SLI bits on release, most games work fine with it. I just wish Nvidia fixed some of the missing new features like MFAA and DSR not working on SLI despite being the perfect platform for those.

For 1080p there are already plenty of cards that can run most games at good framerates.

Those don't work on SLI?

 

[UaVaj]

multi gpu has being reduced, however far from dead.

single gpu performance is catching up to what most folks "want" at 1080p.
single gpu performance is also catching up to what most folks "need" at 1440p.
single gpu performance have YET to catch up to what most folks "want" at 1440p.

as for us folks that "WANT/DEMAND" maxed out setting at 1440p and beyond. multi-gpu is the only solution.

if the next single gpu can ever deliver the performance of 290x x3 (doubtful). will consider moving away from multi-gpu. sadly by then. the next generation of games will require more power. requiring that next generation multi-gpu again.

lastly - XDMA CF is near single gpu fluidity/quality. night and day compare to SLI and CF.





at the end of the day. you can always turn down in game settings.
turn it down far enough and even an iGPU can play any AAA games.
just like console gaming?

 

[5150Joker]

Those don't work on SLI?

Not currently, they're supposed to in a future driver release. And have to give credit where it's due, AMD did great with XDMA and NVIDIA needs to get on that train sooner than later.